Rucete ✏ Chemistry In a Nutshell
Electronegativity and bond polarity
While most organic compounds' bonds are covalent, they differ in form from completely covalent (C-C, C-H) to polar (O-H), where electrons are not shared equally between bound atoms. The difference in electronegativity between the bonded atoms is one measure of bond polarity.
Explanation of Electronegativity
It is a measure of an atom's capacity to attract electrons to itself. The polarity of the bond increases as the difference in electronegativities [Δ(en)] of the bonded atoms increases. The more electronegative bond element has partial negative charge (δ-), whereas the less electronegative one has partial positive charge (δ+). As a result, we may expect that C–C ((en) = 0) bonds are non-polar. In addition, C-O ((en) = 1) or C-Cl ((en) = 0.5) to be polar.
Plus, due to the greater mobility of π-electrons, double bonds are more easily polarized. This means that C=O bond is more polar than a C-O bond.
Ionic bonds such as Sodium chloride are more polar than covalent bonds.